For example, in the information recording medium, such as a CD and a DVD, there are developed a multiple layer or multilayer type, or dual layer type optical disc and so on, in which a plurality of recording layers are stacked or laminated on the same substrate. Then, in the information recording apparatus, such as a CD recorder, for recording information onto such a dual layer type (i.e. two-layer type) optical disc, the information is recorded into a recording layer located on the front or the closest side as viewed from the emission or irradiation side of laser light (referred to as an “L0 layer” in this application, as occasion demands), in a rewritable method or irreversible change recording method by irreversible change recording heat by using heat or the like, by focusing the laser light for recording on the L0 layer. Moreover, the information is recorded into a recording layer located on the rear or the farthest side of the L0 layer as viewed from the irradiation side of the laser light (referred to as an “L1 layer” in this application), in a rewritable method or irreversible change recording method by irreversible change recording heat by using heat or the like, by focusing the laser light on the L1 layer through the L0 layer or the like.
Moreover, in the case where data information is recorded onto this type of optical disc or the like, an optimum recording laser power (referred to as an “optimum recording power” in this application, as occasion demands) is set by an OPC (Optimum Power Control) process, depending on the type of the optical disc and the type and recording rate of the information recording/reproducing apparatus, and so on. That is, the calibration is performed for the recording power. By this, it is possible to realize an appropriate recording operation in response to variation in characteristics of the information recording surface of the optical disc. For example, if the optical disc is loaded and a writing command is inputted, data for test writing is recorded into an OPC area with sequentially changing optical intensity, so that a so-called “test writing process” is performed. In particular, there is disclosed a technology in which the OPC area is provided for each of the two recording layers, and the OPC process is performed for each of the two layers.
In addition, in the case of the two-layer type optical disc, with regard to the detection of the optimum recording power in the L1 layer, it is necessary to properly respond to two types of recording states in the L1 layer through which the laser light is transmitted. This is because, normally, if the L0 layer is already recorded, the light transmittance to the L1 layer of the L0 layer decreases, which increases the value of the optimum recording power. On the other hand, if the L0 layer is unrecorded, the light transmittance to the L1 layer of the L0 layer is relatively high, which reduces the value of the optimum recording power.
Then, as described in a patent document 1 and the like, there is also disclosed a technology in which if the OPC process is performed in the L1 layer, at first, the data information is recorded into the L0 layer, and then, the OPC process is more properly performed in the L1 layer.
Patent document 1: Japanese Patent Application Laying Open NO. 2001-52337